Shift indicators are commonly used on manual transmission vehicles to assist non-expert drivers in determining when it is appropriate to shift the transmission to a higher gear in order to maximize driving fuel economy. A system calibrated such that absolute maximum fuel economy would be obtained if a shift occurs at the point indicated by a shift indicator may exhibit a noticeable sag in axle torque at the shift and therefore result in an unpleasant shift feel to the operator. In such situations, operators quickly learn to ignore the shift indicator thus rendering it ineffective for its intended purpose of maximizing fuel economy. Fuel economy figures required to be displayed on new vehicles for sale in the United States are arrived at through a customer usage weighting of the fuel economy obtained on vehicles tested using the upshift indicator light and fuel economy obtained without using the upshift indicator light. It is therefore desirable to balance the pleasability of the shift at the point indicated by the shift indicator with the fuel economy benefits at that shift point since this will tend to result in higher customer usage, higher actual fuel economy and higher fuel efficiency ratings for a particular vehicle.
Conventional shift indicator calibration typically involves setting manifold absolute pressure (MAP) thresholds at a variety of speeds. Such a method can be time consuming and result in non-optimal shift points. Additionally, as actual engine torque changes due to spark retardation for control of engine knock as may be practiced in the engine control, the calibrated shift points based on MAP thresholds may no longer be appropriate, thereby exacerbating the aforementioned axle torque sag thus leading to operator disregard of the shift indicator and reduced fuel economy.